Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]
Beginning balance, shares at Jan. 02, 2018		43,550,329	2,423,871
Beginning balance at Jan. 02, 2018	$ 35,861	$ 436	$ (35,000)	$ 171,613	$ (101,188)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, warrants and employee stock purchase plan (in shares)		140,066
Proceeds from exercise of stock options, warrants and employee stock purchase plan	(293)	$ 1		(294)
Stock-based compensation expense	1,617			1,617
Net loss	(9,510)				(9,510)
Ending balance at Jul. 03, 2018	26,169	$ 437	$ (35,000)	172,936	(112,204)
Ending balance, shares at Jul. 03, 2018		43,690,395	2,423,871
Beginning balance, shares at Apr. 03, 2018		43,559,312	2,423,871
Beginning balance at Apr. 03, 2018	31,407	$ 436	$ (35,000)	172,240	(106,269)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, warrants and employee stock purchase plan (in shares)		131,083
Proceeds from exercise of stock options, warrants and employee stock purchase plan	(328)	$ 1		(329)
Stock-based compensation expense				1,025
Net loss	(5,935)				(5,935)
Ending balance at Jul. 03, 2018	26,169	$ 437	$ (35,000)	172,936	(112,204)
Ending balance, shares at Jul. 03, 2018		43,690,395	2,423,871
Beginning balance, shares at Jan. 01, 2019		46,353,309	2,423,871
Beginning balance at Jan. 01, 2019	52,681	$ 464	$ (35,000)	198,352	(111,135)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, warrants and employee stock purchase plan (in shares)		155,277
Proceeds from exercise of stock options, warrants and employee stock purchase plan	(235)	$ 1		(236)
Stock-based compensation expense	1,862			1,862
Net loss	(1,413)				(1,413)
Ending balance at Jul. 02, 2019	46,903	$ 465	$ (35,000)	199,978	(118,540)
Ending balance, shares at Jul. 02, 2019		46,508,586	2,423,871
Beginning balance, shares at Apr. 02, 2019		46,370,951	2,423,871
Beginning balance at Apr. 02, 2019	45,596	$ 464	$ (35,000)	199,110	(118,978)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from exercise of stock options, warrants and employee stock purchase plan (in shares)		137,635
Proceeds from exercise of stock options, warrants and employee stock purchase plan	(256)	$ 1		(257)
Stock-based compensation expense	1,125			1,125
Net loss	438				438
Ending balance at Jul. 02, 2019	$ 46,903	$ 465	$ (35,000)	$ 199,978	$ (118,540)
Ending balance, shares at Jul. 02, 2019		46,508,586	2,423,871